This invention relates to implantable wireless devices and methods for using such implants in a body.
A number of approaches exist for retrieving electrical or magnetic signals from the brain of animals and/or humans by use of different neural sensor probes. These may reside outside a subject's head (as in EEG, MEG and fMRI), in a space between the skin and the skull, or below the skull either directly atop the brain or penetrating into the brain. The probes below the skull that reside atop the brain are herewith denoted as electrocorticographic (ECoG) arrays, while those where the individual sensor elements penetrate the brain tissue are denoted as multielectrode arrays (MEAs). While invasive, ECoG and MEAs offer considerably more detailed information about the neural circuit functions than EEG-based approaches. In particular, MEAs have been shown to enable extraction of neural circuit signals with spatial and temporal resolution, in which each individual element (microelectrode) of the array reports from a single neural cell, thereby enabling the retrieval of highly function-specific information. An example would be retrieving information from one hundred neurons whose coordinated operation can issue a specific command for the motion of an arm, hand, or finger.
Considering that the outer skin of a human or animal subject is a protective envelope against the environment, any brain sensors implanted or applied below the skin is considered to be “invasive.” Both ECoG and MEA multielectrode implants are examples of invasive probes. With such probes, one major technical challenge is the retrieval of brain signals generated as electrical impulses by appropriate electronic acquisition instrumentation for further interpretation denoted here as decoding. The electronic acquisition instrumentation typically includes analog circuits for signal amplification from the sensor arrays, their subsequent multiplexing (to serialize the data), conversion to digital data stream (A/D conversion), and transmission of the digitized neural data for subsequent signal processing and use. Signal processing involves decoding strategies which employ mathematical models to interpret and convert the brain signals to useful electronic commands that can operate such devices as robotic arms, typewriters, or other external devices directly from commands issued by the subject's brain.